Business and Geographic Segments - Net Sales by Point of Origin and Point of Destination (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net sales	$ 414.1	$ 475.2	$ 528.6	$ 479.6	$ 388.7	$ 455.2	$ 510.2	$ 466.0	$ 1,897.5	$ 1,820.1	$ 1,879.4
Point of Origin
Segment Reporting Information [Line Items]
Net sales									1,897.5	1,820.1	1,879.4
Point of Destination
Segment Reporting Information [Line Items]
Net sales									1,897.5	1,820.1	1,879.4
United States | Point of Origin
Segment Reporting Information [Line Items]
Net sales									1,164.8	997.6	992.3
Germany | Point of Origin
Segment Reporting Information [Line Items]
Net sales									883.6	886.1	918.6
Canada | Point of Origin
Segment Reporting Information [Line Items]
Net sales									328.7	307.2	309.2
Belgium | Point of Origin
Segment Reporting Information [Line Items]
Net sales									270.7	272.2	279.9
Norway | Point of Origin
Segment Reporting Information [Line Items]
Net sales									192.2	209.6	216.4
North America | Point of Destination
Segment Reporting Information [Line Items]
Net sales									740.1	698.7	668.3
Europe | Point of Destination
Segment Reporting Information [Line Items]
Net sales									824.2	817.6	899.2
Asia and other | Point of Destination
Segment Reporting Information [Line Items]
Net sales									333.2	303.8	311.9
Geography Eliminations | Point of Origin
Segment Reporting Information [Line Items]
Net sales									$ (942.5)	$ (852.6)	$ (837.0)